1. Field of the Invention
The present invention relates to an imaging device which includes a pixel region including a plurality of pixel elements and imaging an incident light of an object as an image and a driving method thereof.
2. Description of the Related Art
As a conventional imaging device capable of imaging a wide imaging area with low resolution and imaging a predetermined partial imaging area with high resolution, there is, for example, Japanese Patent Application Laid-Open No. H09-214836 and Japanese Patent Application Laid-Open No. 2000-032318.
In Japanese Patent Application Laid-Open No. H09-214836, an imaging device capable of reading data of a predetermined pixel element is used. And a block mode for reading only the pixel element of a predetermined block among all pixel elements, and a skip mode for reading all pixel elements at a predetermined thinning-out rate are switched to drive, write in memory and display. Thereby, an imaging device capable of implementing adjustment of angle of view prior to imaging and image display for focusing rapidly and accurately is provided. Moreover, an imaging device capable of making a fully-displayed image on one display with short recurrence cycle and an image displayed in a partially-enlarged manner viewable at the same time is provided.
In addition, in Japanese Patent Application Laid-Open No. 2000-032318, an imaging device comprising a solid-state imaging device having a two-dimensional pixel array and made to scan in a plurality of scanning modes has been disclosed. This imaging device scans all pixel elements only of a pixel group of a continued predetermined region in the pixel array of the solid-state imaging device. Moreover, this imaging device comprises a scan control unit scanning the pixel group in the remaining region of the pixel array in a thinning out manner and a video signal separating unit separating a video signal from the entire pixel scanning region and a video signal from a thinning out scanning region each other. Thereby, an imaging device capable of obtaining from the same frame entire image information by thinning out scanning and high resolution partial image information by entire pixel scanning at the same time is provided.
However, the above described two patent documents respectively include the following problems. At first, the imaging device described in Japanese Patent Application Laid-Open No. H09-214836 uses the same pixel element at the occasion of reading an image in low resolution and reading an image in high resolution. Therefore, also in the case of reading a frame in low resolution and a frame in high resolution alternately, accumulation and pixel reading have to be carried out chronologically for each frame to consequently reduce the effective frame rate, giving rise to a problem.
In addition, the imaging device described in Japanese Patent Application Laid-Open No. 2000-032318 will obtain an image in low resolution and an image in high resolution from the same frame. Therefore, exposure control or the gain of each pixel element has to be adjusted on each image and, therefore, change in driving timing of a sensor becomes complicated, giving rise to a problem.
Moreover, both of the above described imaging devices are not considered on the driving frequency at the time of image reading; a frame rate of each image will be change in the case where a plurality of images in high resolution are read, giving rise to a problem.